David Rauschenbach

"This old man", continued Bogga-Eddin, "is a member of a brotherhood, known among the dervishes by the name of Sarmoung, of which the chief monastery is somewhere in the heart of Asia."

...

I had several long conversations with this old man. In the last one he advised me to go to his monastery and stay there for a time.

...

He added that if I wished to go there, he would be willing to help me, and would find the necessary guides, on condition that I would take a solemn oath never to tell anyone where the monastery was situated.